The number of sweeteners lining supermarket shelves is mind-boggling. There are artificial sweeteners, natural sweeteners and sweeteners with names too difficult to pronounce.

There is not a whole lot of consensus on which one is better for you, or even the least harmful. Too much sugar will make you fat, the experts say. On the other hand, too much zero-calorie artificial sweetener can also make you fat, others argue.

Being overweight can lead to heart disease, diabetes and other serious health problems. Even if sugar substitutes don't make you fat, at one time or another they have been linked to cancer and headaches. But, the National Cancer Institute says there is no clear evidence that artificial sweeteners available in the United States are associated with cancer risk in humans.

Jo Ann Hattner, a registered dietitian and teacher at Stanford School of Medicine, says there are a lot of pros to using artificial sweeteners, especially for those with diabetes or prone to obesity. She says as long as they're used in moderation, they could be better than sugar. A Harvard study tends to agree, finding that the use of aspartame aided in weight loss.

But scientists at Purdue University found the opposite. Their 2008 study found that artificial sweeteners could actually make people gain weight. The study suggests that zero-calorie sugar substitutes have a potential to trick the mind, taking away the ability to link the taste of sweetness with calories.

Here's a look at some of the most popular sweeteners on the market and the pros and cons.

Sucrose

Most commonly known as table sugar, this comes from refining either sugar cane or sugar beets.

Sucrose is a chemical combination of glucose and fructose. Fructose is the sweeter of the two, says Dr. George Bray, a Bay Area author of "The Low-Fructose Approach to Weight Control" and an obesity expert. Although it's found in fruit and some vegetables, what Bray calls "good fructose," when it's refined and used in processed foods it's no longer useful - in fact it's nothing more than empty or useless calories, he says. By avoiding "bad fructose," you'll be cutting down on higher-fat and highly processed foods, Bray advises.

A teaspoon of sugar has 15 calories and 4 grams of carbohydrates. The U.S. Department of Agriculture recommends that added sugar (not what we get from fruit and vegetables) account for less than 25 percent of our daily calories. Many nutritionists argue that it should be even less, Bray says.

"We can live without any bad fructose and in fact would be better off if we did," he says.

Dr. Robert Baron, a professor of medicine and an associate dean at UC San Francisco, agrees that there's not much good to say about sugar. Besides packing calories, sucrose causes tooth decay.

But Baron says he would be in favor of using a little sugar, rather than zero-calorie artificial sweeteners - specifically when weight or diabetes is not an issue - if it's the only way to get children and adults to eat more healthful foods. Example: Sprinkling a little sugar on a grapefruit. The doctor says that at least sugar has some natural component and isn't as sweet as sugar substitutes. There is some thought that sweetness can be addictive.

But when it comes to soft drinks, Baron advocates diet soda, saying there is a direct correlation between the obesity crisis in this country and the consumption of pop.

Realistically, the experts say, it's pretty difficult to completely give up sugar unless it's life threatening. What we can tell you from much experimentation in The Chronicle's test kitchen is that nothing compares to cane sugar for flavor and texture in baking (see recipes).

High-fructose corn syrup

Many point to high-fructose corn syrup as being largely responsible for the American obesity problem. Because it's cheaper than sugar, has a longer shelf life, makes food moister and protects against freezer burn, food manufacturers began using the sweetener in everything from baked goods and sauces to candy and soda starting in the late 1970s.

Not long afterward, Americans started gaining weight. But some believe that it's more likely that Americans eat too much processed foods and that high-fructose corn syrup is no worse than sugar, just used more frequently.

The sweetener has also been accused of contributing to the risk of diabetes. But scientists say the allegation is a bit misleading. There is a correlation between excess weight and diabetes, but weight gain can come from eating too much fat or other high-calorie foods. There is some research that suggests fructose might lead to leptin resistance, a feature of diabetes, which scientists are continuing to study.

Although the Corn Refiners Association has advertised high-fructose corn syrup as a natural product, doctors and scientists say it's not.

"High-fructose corn syrup does not exist in nature - it is man-made," Bray writes in his book.

It's made from corn syrup by using enzymes to convert its glucose to fructose. It contains the same amounts of calories and carbohydrates as sugar and is similar in flavor and sweetness.

According to the Corn Refiners Association, high-fructose corn syrup enhances fruit and spice flavors and is particularly good for browning baked goods and reducing sugar crystallization. But it's not a product that's readily available to the home cook.

Agave syrup

The sweetener that comes from a Mexican plant - the same one used to produce Tequila - is making quite a stir. Agave syrup or nectar is being used to sweeten teas, energy drinks, protein bars and pastries.

Its calorie and carbohydrate content is similar to that of sugar, but because it's about three times sweeter, you can use less. Unlike sucrose, agave can be up to 90 percent fructose, depending on how it's processed. The higher it is in fructose, the less likely it is to raise blood glucose levels, which is helpful to diabetics.

Oddly, scientists believe that fructose has the lowest glycemic index, a ranking system for carbohydrate foods based on their effects on blood glucose levels, of all sugars. This seems somewhat contradictory given that fructose is so often linked to obesity.

Although agave may seem like a safer choice for diabetics, experts warn to use it with caution. There is not enough scientific evidence yet to recommend it as a dietetic substitute.

While agave is seen by many consumers as a healthful alternative to sucrose and high-fructose corn syrup, experts say don't let it fool you - it's sugar, plain and simple.

Its flavor benefits are that it sweetens without changing the flavor of other ingredients. And while it doesn't work with everything, agave is a fine substitute for sweetening tea, cereal and yogurts. Its best use that we know of: replacing the simple syrup in a margarita.

Stevia

This is a natural sweetener that has zero calories and zero carbohydrates, and is as much as 300 times sweeter than sugar. Its brand names include Truvia, PureVia, SweetLeaf, Stevia Extract in the Raw and Sun Crystals sugar-stevia blend.

The sweetener is derived from a plant in the chrysanthemum family that grows wild in Latin America. Its first reported use dates to the 1800s and is still widely used in Japan.

In 2008, the Food and Drug Administration approved the use of a highly purified form of stevia known as rebaudioside A as a food additive. Stevia had been previously banned after some laboratory tests on animals found that it caused possible cancer mutations or reproductive problems. Flaws were eventually found with the study and the ban was lifted, despite urging from the Center for Science in the Public Interest, a nonprofit watchdog group, for additional testing.

There are some foreign studies that suggest stevia can lower blood pressure in people with mild hypertension and reduce blood glucose levels in people who have Type 2 diabetes.

Both the Coca-Cola Co. and PepsiCo Inc. have announced plans to use the sweetener in their drinks in hopes of increasing sales of a product that's received much criticism for enlarging the American waistline.

As far as flavor, stevia tends to have a bit of a black licorice finish.

Xylitol

Although our tasters (see Taster's Choice, Page K2) found this to have the best flavor of all the sucrose substitutes, it shouldn't be eaten in large amounts. Its side effects are gas, bloating and diarrhea. The good news is that it doesn't cause tooth decay.

Xylitol is a sugar-alcohol sweetener derived from birch and other hardwood trees, berries, almond hulls and corn cobs. It has the same sweetness as sugar and the same amount of carbohydrates per teaspoon, but fewer calories - about 9.6.

Although Xylitol is promoted as safe for diabetics, the American Diabetes Association recommends caution. "The effect that sugar alcohols have on your blood glucose can vary so it is difficult to know how sugar alcohols will affect your blood glucose levels every time," the association says.

Saccharin

This artificial sweetener includes brands such as Sweet'N Low and Sweet Twin. It's 200 to 700 times sweeter than sugar and has zero calories. It's been around for more than 100 years, and some experts believe it is the safest of all the artificial sweeteners, possibly because it's been the most researched.

In the early 1970s, studies using laboratory rats linked saccharin to bladder cancer. Congress ordered more studies and required food containing saccharin to carry a warning label. But after more than 30 human studies, scientists found the cancer results applied only to rats. Since then, the warning has been lifted.

Some complain of saccharin's bitter aftertaste, and although manufacturers say you can bake with it, our results in the past have not been good.

Aspartame

An artificial sweetener sold by brand names such as Equal, NutraSweet and NatraTaste. It's up to 200 times sweeter than sugar and is virtually calorie-free (about 4 kilocalories per gram). It was discovered in 1965 and approved by the FDA in 1981.

In 1996, questions about its safety arose when a correlation was suggested between its use and the increase in the number of people with brain tumors. But statistics showed that the surge in brain and central nervous system cancers began to rise eight years before the approval of aspartame. Later, a study found that when rats were fed high doses of aspartame, the equivalent of more than eight cans of diet soda, they were more likely to have lymphomas and leukemias. But there were inconsistencies with those findings.

Scientists at the American Diabetes Association and other groups believe aspartame is safe. Common complaints include that it causes headaches and has a chemical flavor. It's not recommended for baking.

Sucralose

Sold as Splenda, this artificial sweetener is up to 600 times sweeter than sugar. It contains some calories, but because such small amounts are needed, it can be classified as a zero-calorie sweetener. It was approved by the FDA as a tabletop sweetener in 1998 and as a general-purpose sweetener a year later.

Because Splenda is relatively new, there are fewer studies. It does enjoy some controversy over the fact that it was discovered during the process of developing an insecticide.

It's one of only two sweeteners deemed safe by the Center for Science in the Public Interest. The other is Neotame, an artificial sweetener that was approved by the FDA in 2002 but is rarely used.

Many find that sucralose is the most natural tasting of all the artificial sweeteners on the market. It can be used for baking, but we didn't much care for the results.

-- Taster's Choice on sweeteners. K2

-- Recipes and a guide to different sweeteners. K4

The cookie bake-off test

To compare how various sweeteners worked, we did a bake-off in The Chronicle's test kitchens using one of our favorite cookie recipes, the Cherry Chocolate Chunk Cookies that staff writer Amanda Gold developed for a 2009 holiday issue.

The differences were substantial.

The original recipe was the most mouth watering- the cookies had a tender crumb, crunchy exterior and slightly gooey interior. When baked, they expanded outward instead of upward, in traditional cookie fashion.

The agave cookie reminded the Food & Wine staff of a scone or muffin top. The texture was fluffy and airy; the flavor was not overwhelmingly sweet - a plus, everyone agreed. Interestingly, the agave cookie tasted better the next day.

The stevia cookie, though not even close to being the favorite, worked well for a sugar fix. It didn't brown normally when baking, which made it hard to tell when it was done. The texture was somewhat chalky and dry, but acceptable. If sugar is something you cannot have in your diet, this cookie might be your new best friend.

- Kalena Ross

Cherry Chocolate Chunk Cookies

Makes 3 1/2 dozen cookies

This traditional cookie recipe, using white and brown sugars, can be varied by replacing the sugars with either stevia or agave.

2 sticks butter, softened

3/4 cup granulated sugar

3/4 cup packed brown sugar

1 teaspoon kosher salt

2 eggs

1 1/2 teaspoons vanilla extract

1 teaspoon baking soda

2 1/2 cups all-purpose flour

10 ounces dark chocolate chunks

2/3 cup dried cherries

Instructions: Preheat oven to 350°.

In the bowl of an electric mixer fitted with a paddle attachment, cream the butter, sugars and salt until light and fluffy, about 2-3 minutes. Add eggs, one at a time, then the vanilla, beating after each addition. Slowly add in the baking soda and flour, beating until well combined, taking care not to over mix. With a spatula, fold in the chocolate chunks and cherries.

Using 2 tablespoons or a small ice cream scoop, form cookies and place, 2 inches apart, on ungreased baking sheets. Bake 10 minutes or until light golden brown.